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NK does NOT and did NOT have nuclear bombs.

From The Nuclear Weapon Archive: A Guide to Nuclear Weapons:

On the morning of 9 October 2006 North Korea informed the Chinese government that they should expect a four kiloton nuclear test. Twenty minutes later, at 01:35:28 UTC, a seismic event occurred at 41.294 degrees N latitude, 129.094 degrees E longitude, with a magnitude of 4.2, according to the U.S. Geological Survey. The test was followed by a public declaration of success by the North Korean government.
Although the initial USGS data provided a position uncertainty of 7 kilometers, it placed the site approximately 42 kilometers northwest of Kilchu, in Hwaseong-gun, North Hamgyeong Province. This coincides with a site of suspicious tunneling and construction activities that were first reported in 2005, on the east slope of remote 7231 feet high Mant'ap-san Mountain. Subsequent reports during the past month indicate that the North Koreans had excavated a 700 m-long horizontal tunnel under Mant'ap-san. An unpaved road extends 19 km from the test site to the nearest town of Punggye-ri along the Namdae River.
The Korea Institute of Geoscience & Mineral Resources (KIGAM), South Korea's state-run geoscience institute, adjusted its estimate of the epicenter on 13 October to 41.26 degrees N latitude and 129.17 degrees E longitude.
Two measurements of the seismic magnitude of the test have been published: magnitude 4.2 by the USGS, and between 3.58 and 3.7 by the KIGAM. An uncertainty in seismic magnitude of 0.5 translates into an uncertainty in yield of about a factor of three. Compounding this uncertainty is that relationship between seismic magnitude and yield which depends upon the hardness of the rock in which the explosive is buried.
The explosive yield has been estimated by Terry Wallace, a seismologist at Los Alamos National Laboratory, to be between 0.5 and 2 kilotons, with 90 percent confidence that the yield is less than 1 kiloton. Lynn R. Sykes of Columbia University estimates a yield of 0.4 kilotons, with 68 percent confidence that the yield is between 0.2 and 0.7 kilotons and a 95 percent probability that the yield is less than 1 kiloton. Other published median yield estimates have been 500 and 550 tons ([Garwin and von Hippel 2006]).
The test was conducted deep underground in a horizontal tunnel which prevented the immediate or large scale release of radioactivity. Nonetheless a high percentage of underground nuclear tests leak detectable levels of radioactivity, most reliably radioactive isotopes of the inert gases krypton and xenon, which can leak through natural or blast induced fissures in the surrounding rock driven by the high pressures resulting from the explosion. Leaks can be become detectable at the surface on a time scale ranging from tens of minutes to days ([Adushkin and Leith 2001]).
Atmospheric sampling missions flown by the Air Force's specialized WC-135 Constant Phoenix, the last Cold War era "sniffer" plane still in service, were begun by the United States shortly after the test. On 13 October it was reported that traces of radioactivity had been detected and on 16 October National Intelligence Director John Negroponte's office released a statement confirming that samples collected on 11 October showed that the test was indeed a nuclear blast, laying to rest some initial speculation that the low yield explosion might in fact be simply a very large conventional explosive blast.
Subsequent analysis of samples has shown that the fissile material used in the test was plutonium. Since different fissile materials produce different proportions of various radionuclides, measuring these ratios (such as the ratios of Xe-133, Xe-133m and Xe-135) can unambiguously determine the fissile material used. Leaks of additional isotopes which can occur would make the determination even easier.
[...]
Garwin and von Hippel report that if radioxenon leaked into the atmosphere at a rate of only 0.1 percent a day, a concentration of 10,000 atoms per cubic meter of air would be detectable downwind three days after the test, one hundred times the detectability threshold. If the isotope ratio of about 8000 radioxenon atoms could be measured, then the identity of the fissile parent could be established as being plutonium with 95 percent certaintly ([Garwin and von Hippel 2006]).
The North Koreans have high grade plutonium (content of neutron emitting Pu-240 measured at 2.44% by the IAEA in the July 1992, compared to 6% for U.S. weapons plutonium), so problems with predetonation are almost certainly not the cause.([May 2001])
The low yield, almost certainly less than a quarter of its reported planned yield, indicates a partial failure of the device. The most likely cause is poor implosion performance (that is, poor compression), though late initiation is also a possibility.
Regarding the possibility of poor compression, it should be observed that they are likely trying to develop a relatively sophisticated light system suitable for missiles, in the range of 500-1000 kg, not the 3500 kg design of the WWII Fat Man, which proved very reliable. Failure might be due to problems perfecting the design, or simply some test-related technical fault in an otherwise sound design.
The relatively low yield announced prior to the test was possibly to conserve plutonium of which North Korea has a fairly limited supply. [Source]

WHY NORTH KOREA’S NUKE TEST IS SUCH GOOD NEWS
Written by Dr. Jack Wheeler
Tuesday, 10 October 2006

The public face of Bush Administration officials regarding North Korea's nuclear test is a mask of utter seriousness, or "grave concern." Behind the mask, folks are laughing their heads off. Meanwhile, the world's dumbest nuclear scientists - namely, those in North Korea - are terrified of what Baby Kim will do to them when he finds out the truth.

Essentially, we have a replay of the total fiasco of Baby Kim's headline-garnering missile test launch last July. In Climbing Fujiyama, you learned that:

The public reaction by both the Japanese and American governments - serious anger - is tempered by the private one. In the White House and the Kokkai (Japanese Parliament), there is a lot of laughter. GW really had to suppress his smirk in a press conference when he noted that the dreaded Taepodong-2 (which the press calls an "Intercontinental Ballistic Missile capable of reaching the US with its 6,000 kilometer range") blew up 40 seconds after launch.

"What a bunch of bozos," is the private assessment here in Tokyo and in DC. "All their missiles failed. It's even more of a spectacular flop than their Taepodong-1 test back in 1998, where the first two stages went off ok until the third stage blew up. These clowns can now barely get their popguns off the launch pad."

Yet everyone has to bite their tongues and resist the overwhelming temptation to publicly ridicule the North Koreans and laugh in Baby Kim's face. Doing so would make it much harder to get international sanctions on Pyongyang.

You have to become a member over at Wheeler's site to read the rest....